TECHNICAL FIELD
[0001] The present disclosure relates generally to a cooled cooling air system for a gas
turbine engine, and more specifically to an injection cooling system for the same.
BACKGROUND
[0002] Gas turbine engines include a compressor section that compresses air, a combustor
that mixes the compressed air with a fuel and ignites the mixture, and a turbine section
across which the resultant combustion products are expanded. As a result of the compression,
combustion, and expansion process, areas of the gas turbine engine, including portions
of the flowpath such as the combustor, the high pressure turbine, and the high pressure
compressor are exposed to extreme temperatures. In order to mitigate the extreme temperatures,
components exposed to the flowpath are, in some examples, actively cooled by providing
a coolant to the component.
[0003] In such examples, the coolant can be extracted from sources within the gas turbine
engine, such as the compressor outlet, or a mid-stage of the compressor via a compressor
bleed. For certain engine cycles, depending on the position within the primary flowpath
that the coolant is bled from, the temperature of the coolant can be too high to effectively
cool the component that the coolant is being directed to. To remedy this, the coolant
is actively cooled, and the system is referred to as a cooled coolant system.
[0004] In a typical example cooled coolant system, the coolant is passed through a physical
heat exchanger, where the coolant is cooled via conventional heat exchange. Heat exchangers
of this type are large and can incur substantial monetary costs, weight increases
and performance losses on the gas turbine engine. Further exacerbating these losses
is the fact that the cooling demand is not fixed throughout the flight cycle, and
during portions of the flight the additional cooling is not actively needed.
SUMMARY OF THE INVENTION
[0005] From a first aspect, there is provided a gas turbine engine that includes an engine
core having a compressor section, a combustor fluidly connected to the compressor
section, and a turbine section fluidly connected to the combustor section, at least
one compressor bleed connecting a compressor flowpath with a first cooled cooling
air path, the first cooled cooling air path including a supplementary coolant injector
connected to a supplementary coolant supply, the cooled cooling air path including
a portion exterior to the engine core.
[0006] In an exemplary embodiment of the above described gas turbine engine the supplementary
coolant injector is exterior to the engine core.
[0007] In another exemplary embodiment of any of the above described gas turbine engines
the at least one compressor bleed is disposed at a compressor outlet.
[0008] In another exemplary embodiment of any of the above described gas turbine engines
at least a first compressor bleed of the at least one compressor bleed is disposed
at a mid-compressor stage.
[0009] In another exemplary embodiment of any of the above described gas turbine engines
at least a second compressor bleed of the at least one compressor bleed is disposed
at a compressor outlet.
[0010] In another exemplary embodiment of any of the above described gas turbine engines
the supplementary coolant is configured to cool coolant in the cooled cooling air
path at least partially via expansion of the supplementary coolant.
[0011] In another exemplary embodiment of any of the above described gas turbine engines
the supplementary coolant injector comprises a plurality of supplementary coolant
ports, each of the supplementary coolant ports being configured to inject a portion
of the supplementary coolant into the cooled cooling air path.
[0012] In another exemplary embodiment of any of the above described gas turbine engines
the at least one compressor bleed comprises at least a first compressor bleed connected
to the cooled cooling air path and a second compressor bleed connected to a second
cooled cooling air path, and wherein a supplementary coolant connected to the first
cooled cooling air path is a liquid, and a supplementary coolant connected to the
second cooled cooling air path is a compressed gas.
[0013] In another exemplary embodiment of any of the above described gas turbine engines
the supplementary coolant is configured to cool coolant in the cooled cooling air
path at least partially via a state change of the supplementary coolant.
[0014] Another exemplary embodiment of any of the above described gas turbine engines further
includes an engine controller controllably coupled to the supplementary coolant injector
and configured to control injection of the supplementary coolant through the supplementary
coolant injector.
[0015] In another exemplary embodiment of any of the above described gas turbine engines
the controller includes a memory storing instructions configured to cause the controller
to operate the injector at a first injection level during a first engine mode of operations,
and at a second injection level during a second mode of engine operations.
[0016] In another exemplary embodiment of any of the above described gas turbine engines
the cooled cooling air path includes a heat exchanger configured to cool bleed air
passing through the cooled cooling air path.
[0017] In another exemplary embodiment of any of the above described gas turbine engines
a supplementary coolant contained in the coolant supply comprises at least one of
a compressed gas, water, liquid nitrogen, liquid CO2, and liquid air.
[0018] There is also provided a method for cooling air in a cooled cooling air system that
includes injecting at least a first supplementary coolant into a first cooled cooling
air path, and thereby cooling a coolant passing through the cooled cooling air path,
the supplementary coolant including a compressed gas and providing the cooled cooling
air to at least one flowpath component of a gas turbine engine.
[0019] In an example of the above described exemplary method for cooling air in a cooled
cooling air system injecting at least the first supplementary coolant into the first
cooled cooling air path, further comprises injecting a second supplementary coolant
into a second cooled cooling air path.
[0020] In another example of any of the above described exemplary methods for cooling air
in a cooled cooling air system the first supplementary coolant includes a compressed
gas, and the second supplementary coolant is one of a compressed gas distinct from
the first compressed gas and a liquid.
[0021] Another example of any of the above described exemplary methods for cooling air in
a cooled cooling air system further includes receiving coolant into the first cooled
cooling air path from at least one compressor bleed.
[0022] In another example of any of the above described exemplary methods for cooling air
in a cooled cooling air system the compressor bleed is one of a mid stage compressor
bleed and a compressor outlet bleed.
[0023] Another example of any of the above described exemplary methods for cooling air in
a cooled cooling air system further includes cooling air in the first coolant path
using a heat exchanger.
[0024] Another example of any of the above described exemplary methods for cooling air in
a cooled cooling air system further includes varying an amount of the first supplementary
coolant injected into the first cooled cooling air path using a controller, with the
amount of coolant injected being dependent upon a current engine mode of operations.
[0025] These and other features of the present invention can be best understood from the
following specification and drawings, the following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026]
Figure 1 illustrates an exemplary gas turbine engine.
Figure 2 schematically illustrates a portion of the gas turbine engine including a
first exemplary cooled cooling air system.
Figure 3 schematically illustrates a portion of the gas turbine engine including a
second exemplary cooled cooling air system.
Figure 4 schematically illustrates a portion of the gas turbine engine including a
third exemplary cooled cooling air system.
Figure 5 schematically illustrates a portion of the gas turbine engine including a
fourth exemplary cooled cooling air system.
DETAILED DESCRIPTION OF AN EMBODIMENT
[0027] Figure 1 schematically illustrates a gas turbine engine 20. The gas turbine engine
20 is disclosed herein as a two-spool turbofan that generally incorporates a fan section
22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative
engines might include an augmentor section (not shown) among other systems or features.
The fan section 22 drives air along a bypass flow path B in a bypass duct defined
within a nacelle 15, while the compressor section 24 drives air along a core flow
path C for compression and communication into the combustor section 26 then expansion
through the turbine section 28. Although depicted as a two-spool turbofan gas turbine
engine in the disclosed non-limiting embodiment, it should be understood that the
concepts described herein are not limited to use with two-spool turbofans as the teachings
may be applied to other types of turbine engines including three-spool architectures.
[0028] The exemplary engine 20 generally includes a low speed spool 30 and a high speed
spool 32 mounted for rotation about an engine central longitudinal axis A relative
to an engine static structure 36 via several bearing systems 38. It should be understood
that various bearing systems 38 at various locations may alternatively or additionally
be provided, and the location of bearing systems 38 may be varied as appropriate to
the application.
[0029] The low speed spool 30 generally includes an inner shaft 40 that interconnects a
fan 42, a first (or low) pressure compressor 44 and a first (or low) pressure turbine
46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism,
which in exemplary gas turbine engine 20 is illustrated as a geared architecture 48
to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool
32 includes an outer shaft 50 that interconnects a second (or high) pressure compressor
52 and a second (or high) pressure turbine 54. A combustor 56 is arranged in exemplary
gas turbine 20 between the high pressure compressor 52 and the high pressure turbine
54. A mid-turbine frame 57 of the engine static structure 36 is arranged generally
between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine
frame 57 further supports bearing systems 38 in the turbine section 28. The inner
shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about
the engine central longitudinal axis A which is collinear with their longitudinal
axes.
[0030] The core airflow is compressed by the low pressure compressor 44 then the high pressure
compressor 52, mixed and burned with fuel in the combustor 56, then expanded across
the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57
includes airfoils 59 which are in the core airflow path C. The turbines 46, 54 rotationally
drive the respective low speed spool 30 and high speed spool 32 in response to the
expansion. It will be appreciated that each of the positions of the fan section 22,
compressor section 24, combustor section 26, turbine section 28, and fan drive gear
system 48 may be varied. For example, gear system 48 may be located aft of combustor
section 26 or even aft of turbine section 28, and fan section 22 may be positioned
forward or aft of the location of gear system 48.
[0031] The engine 20 in one example is a high-bypass geared aircraft engine. In a further
example, the engine 20 bypass ratio is greater than about six, with an example embodiment
being greater than about ten, the geared architecture 48 is an epicyclic gear train,
such as a planetary gear system or other gear system, with a gear reduction ratio
of greater than about 2.3 and the low pressure turbine 46 has a pressure ratio that
is greater than about five. In one disclosed embodiment, the engine 20 bypass ratio
is greater than about ten, the fan diameter is significantly larger than that of the
low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that
is greater than about five. Low pressure turbine 46 pressure ratio is pressure measured
prior to inlet of low pressure turbine 46 as related to the pressure at the outlet
of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture
48 may be an epicycle gear train, such as a planetary gear system or other gear system,
with a gear reduction ratio of greater than about 2.3:1. It should be understood,
however, that the above parameters are only exemplary of one embodiment of a geared
architecture engine and that the present invention is applicable to other gas turbine
engines including direct drive turbofans.
[0032] A significant amount of thrust is provided by the bypass flow B due to the high bypass
ratio. The fan section 22 of the engine 20 is designed for a particular flight condition
-- typically cruise at about 0.8 Mach and about 35,000 feet (10668 meters). The flight
condition of 0.8 Mach and 35,000 ft (10668 m), with the engine at its best fuel consumption
- also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')" - is the
industry standard parameter of lbm of fuel being burned divided by lbf of thrust the
engine produces at that minimum point. "Low fan pressure ratio" is the pressure ratio
across the fan blade alone, without a Fan Exit Guide Vane ("FEGV") system. The low
fan pressure ratio as disclosed herein according to one non-limiting embodiment is
less than about 1.45. "Low corrected fan tip speed" is the actual fan tip speed in
ft/sec divided by an industry standard temperature correction of [(Tram °R) / (518.7
°R)]^0.5 (where °R = K x 9/5). The "Low corrected fan tip speed" as disclosed herein
according to one non-limiting embodiment is less than about 1150 ft / second (350.5
m/s).
[0033] Combustion within combustor section 26, and expansion across the turbine section
28, generates extreme levels of heat, and exposes components at or near the combustor
section 26 and turbine section 28, and in contact with the flowpath, to the high levels
of heat. In alternative examples, any component within the turbine engine core can
be exposed to the high levels of heat. As used herein, the turbine engine core refers
to the compressor section 24, combustor section 26 and the turbine section 28, as
well as the inner and outer radial structures that define the compressor section 24,
combustor section 26 and turbine section 28. Turbine engine components exposed to
the primary flowpath are referred to herein as "flowpath components". In some examples,
the magnitude of heat to which the flowpath components are exposed is in excess of
the heat capabilities of the flowpath component. In such examples, the flowpath components
are actively cooled, in order to maintain the temperature of the flowpath component
below a maximum temperature to which the component can be exposed without suffering
damage. One way of sourcing the coolant for the flowpath components is to remove (bleed)
air from within the compressor section 24, either at a mid-compressor bleed or at
a compressor outlet, and duct the bleed air to a cooling circuit of the flowpath component
being cooled.
[0034] With continued reference to Figure 1, Figure 2 schematically illustrates a portion
100 of a gas turbine engine including a first exemplary cooled cooling air system
110. The illustrated portion 100 of the gas turbine engine includes a compressor section
102, a combustor section 104 and a turbine section 106. A compressor bleed 120 is
included at an outlet of the compressor section 102 and provides a portion of the
compressed air output from the compressor section 102 to the cooled cooling air system
110. The cooled cooling air system 110 ducts the bleed air to an input port 130 of
a cooling circuit of a flowpath component at, or near, a last stage of the compressor
section 102. In alternative examples, the cooled cooling air can be provided to a
flowpath component at any other position within the compressor section 102.
[0035] The cooled cooling air system 110 further includes a supplementary coolant injector
140. The supplementary coolant injector 140 is configured to inject a supplementary
coolant, such as a liquid or a compressed gas, into the cooled cooling air system
110. Injection of the supplementary coolant reduces the temperature of the bleed air,
allowing the bleed air to be utilized to cool a flowpath component. In some examples,
such as the liquid supplementary coolant examples, the supplementary coolant operates
to cool the bleed air at least in part via a phase change, where the liquid coolant
is converted into a gas. In other examples, such as a compressed gas supplementary
coolant example, the expansion of the supplemental coolant can contribute to, and
enhance, the cooling within the cooled cooling air system 110.
[0036] The supplementary coolant is provided to the injector 140 from a supplementary coolant
source 150. The supplementary coolant source 150 is disposed within the engine housing.
In the case of a liquid supplementary coolant, the supplementary coolant source 150
can be a liquid reservoir. In the case of a compressed gas supplementary coolant,
the supplementary coolant source can be a pre-charged canister, a supplementary compressor,
a gas generator, or any similar construction. The injector 140 is connected to the
supplementary coolant source 150 via any known connection suitable for the fluid type
of the supplementary coolant.
[0037] In some examples, the cooled cooling air is sufficient to cool the receiving flowpath
component, without requiring supplementary coolant injection in some modes of engine
operation, but requires supplementary coolant injection in other modes of engine operation.
In such an example, a controller 160 can control the injector 140 using any known
injection control, such that supplementary coolant is provided to the cooled cooling
air system 110 only during modes of engine operation where the supplementary coolant
is required. Further, in some examples, the amount of supplementary coolant required
can vary depending on the mode of operation in which the engine is operating. In such
examples, the controller 160 can vary the volume of supplementary coolant provided
to the cooled cooling air path and/or vary the frequency with which the supplementary
coolant is provided to the cooled cooling air system 110.
[0038] With continued reference to Figure 2, and with like numerals indicating like elements,
Figure 3 illustrates another exemplary portion 200 of a gas turbine engine including
a first exemplary cooled cooling air system 210. The illustrated portion 200 of the
gas turbine engine includes a compressor section 202, a combustor section 204 and
a turbine section 206 defined within an engine core 201. A compressor bleed 220 is
included at a mid-stage of the compressor section 202. The compressor bleed 220 removes
a portion of the compressed air at the corresponding stage of the compressor section
202 and provides the removed (bleed) air to the cooled cooling air system 210. The
cooled cooling air system 210 includes a portion that extends outside of the engine
core 201. The cooled cooling air system 210 ducts the bleed air to an input port 230
of a cooling circuit of a flowpath component at, or near, a mid-stage of the turbine
section 206. In alternative examples, the cooled cooling air can be provided to a
flowpath component at any other position within the turbine section 206, including
flowpath components at the first stage or multiple flowpath components disposed at
multiple stages of the turbine section 206.
[0039] As with the example of Figure 1, in some or all modes of engine operation, the temperature
of the coolant provided from the bleed 220 is too high to sufficiently cool the flowpath
components receiving the cooled cooling air from the cooled cooling air system 210.
In such a case, a supplementary coolant is injected into the cooled cooling air system
210 via a supplementary coolant injector 240. In the illustrated example, the supplementary
coolant injector 240 is positioned exterior to the engine core 201. The supplementary
coolant is stored and/or generated, depending on the type of supplementary coolant
used, in a supplementary coolant reservoir 250. The supplementary coolant reservoir
250 provides the supplementary coolant to the injector 240 via any suitable supplementary
coolant transmission means.
[0040] Further, as with the example of Figure 2, a controller 260 can be controllably coupled
to the injector 240, thereby allowing the supplementary coolant to be provided only
during engine modes of operation where the supplementary coolant is needed, and allowing
the injector 240 to vary the amount of supplementary coolant provided during different
modes of engine operation in which some supplementary coolant is needed.
[0041] With continued reference to Figures 2 and 3, and with like numerals indicating like
elements, Figure 4 schematically illustrates another exemplary portion 300 of a gas
turbine engine including a first exemplary cooled cooling air system 310 and a second
cooled cooling air system 312. The illustrated portion 300 of the gas turbine engine
includes a compressor section 302, a combustor section 304 and a turbine section 306.
A first compressor bleed 320 is included at a mid-stage of the compressor section
302. The first compressor bleed 320 removes a portion of the compressed air at the
corresponding stage of the compressor section 302 and provides the removed (bleed)
air to the first cooled cooling air system 310. The first cooled cooling air system
310 ducts the bleed air to an input port 330 of a cooling circuit of a flowpath component
at, or near, a mid-stage of the turbine section 306.
[0042] A second compressor bleed 322 is provided at an outlet of the compressor section
302. The second compressor bleed removes (bleeds) a portion of the compressed air
output from the compressor section 302, and provides the bleed air to the second cooled
cooling air system 312. The second cooled cooling air system 312 provides the bleed
air to an input port 332 at a first stage of the turbine section 306.
[0043] In alternative examples, the cooled cooling air in either cooled cooling air system
310, 312 can be provided to flowpath components at any other positions within the
turbine section 306, including to multiple flowpath components disposed at multiple
stages of the turbine section 306.
[0044] As with the previous examples, in some or all modes of engine operation, the temperature
of the coolant provided from the bleeds 320, 322 is too high to sufficiently cool
the flowpath components receiving the cooled cooling air from the corresponding cooled
cooling air systems 310, 312. In such a case, a supplementary coolant is injected
into the cooled cooling air systems 310, 312 via supplementary coolant injectors 340,
342. The supplementary coolant is stored and/or generated, depending on the type of
supplementary coolant used, in a supplementary coolant reservoir 350. The supplementary
coolant reservoir 350 provides the supplementary coolant to the injectors 340, 342
via any suitable supplementary coolant transmission means. In some alternative examples,
the first and second cooled cooling air systems 310, 312 can utilize distinct supplementary
coolant types. In such an example, a second supplementary coolant source 352 can also
be included and provides the second type of supplementary coolant in the same manner
as the first supplementary coolant reservoir 350.
[0045] Further, as with the previous examples, a controller 360 can be controllably coupled
to the injectors 340, 342, thereby allowing the supplementary coolant to be provided
only during engine modes of operation where the supplementary coolant is needed, and
allowing the injectors 340, 342 to vary the amount of supplementary coolant provided
during different modes of engine operation in which some supplementary coolant is
needed. Further, each of the injectors 340, 342 is independently controlled, allowing
supplementary coolant to be provided to one, both, or neither of the cooled cooling
air systems at any given time, depending on the particular mode of engine operations.
[0046] With continued reference to Figures 2-4, Figure 5 schematically illustrates a combination
of the example of Figure 2 and the example of Figure 4. The exemplary portion 400
of the gas turbine engine includes a compressor section 402, a combustor section 404,
and a turbine section 406. The exemplary schematic includes a first, second and third,
cooled cooling air system 410, 412, 414. Each cooled cooling air system is connected
to a compressor bleed, 420, 422, 424, and provides cooling air to a corresponding
flowpath component via input ports 430, 432, 434. Supplementary coolant injectors
440, 442, 444 are included in each of the cooled coolant systems 410, 412, 414, and
provide supplementary coolant from at least one of the supplementary coolant reservoirs
450, 452, 454 in quantities depending on the specific mode of engine operations. As
with the previous examples, each of the injectors 440 can be independently controller
via an engine controller 460.
[0047] While illustrated in each of the above examples as providing supplementary coolant
to the corresponding cooled cooling air system at a single schematic injection point,
one of skill in the art will understand that the injectors can include multiple ports,
and injection holes for providing the supplementary coolant to the corresponding cooled
cooling air system. Further, the position of the injector, relative to the flow through
the cooled cooling air system is not limited to the illustrated exemplary positions.
The injectors can be positioned immediately adjacent the bleed, immediately adjacent
the cooled cooling air system outlet, or at any position between the two, depending
on the structural requirements of the engine, and the specific cooling needs of any
given engine system.
[0048] In further examples, one or more included cooled cooling system can include a physical
heat exchanger that provides a set amount of cooling to the cooled cooling air under
all operating conditions, and supplemental coolant can be injected to the cooled cooling
air upstream, or downstream, of the physical heat exchanger according to the above
description.
[0049] While illustrated in Figures 2 and 4 as interior to the engine core, one of skill
in the art will understand that as with Figure 3, some or all of the cooled cooling
air circuit ducting can pass exterior to the engine core, and in such examples the
supplementary coolant injector can be included exterior to the engine core as well.
[0050] It is further understood that any of the above described concepts can be used alone
or in combination with any or all of the other above described concepts. Although
an embodiment of this invention has been disclosed, a worker of ordinary skill in
this art would recognize that certain modifications would come within the scope of
this invention. For that reason, the following claims should be studied to determine
the true scope and content of this invention.
1. A gas turbine engine (20) comprising:
an engine core (201) having a compressor section (24; 102; 202; 302; 402), a combustor
section (26; 104; 204; 304; 404) fluidly connected to the compressor section (24...402),
and a turbine section (28; 106; 206; 306; 406) fluidly connected to the combustor
section (26...404);
at least one compressor bleed (120; 220; 320, 322; 420, 422, 424) connecting a compressor
flowpath with at least one cooled cooling air path (110; 210; 310; 312; 410, 412,
414); and
the at least one cooled cooling air path (110...414) including a supplementary coolant
injector (140; 240; 340; 342; 440, 442, 444) connected to a supplementary coolant
supply (150; 250; 350, 352; 450, 452, 454), said cooled cooling air path (110...414)
including a portion exterior to the engine core (201).
2. The gas turbine engine (20) of claim 1, wherein the supplementary coolant injector
(240) is exterior to the engine core (201).
3. The gas turbine engine (20) of claim 1 or 2, wherein the at least one compressor bleed
(120; 322; 420, 424) is disposed at a compressor outlet.
4. The gas turbine engine (20) of any preceding claim, wherein at least a first compressor
bleed (220; 320; 422) of the at least one compressor bleed (120...424) is disposed
at a mid-compressor stage, optionally wherein at least a second compressor bleed (322;
420; 424) of the at least one compressor bleed (120...424) is disposed at a compressor
outlet.
5. The gas turbine engine (20) of any preceding claim, wherein a supplementary coolant
is configured to cool coolant in said at least one cooled cooling air path (110...414)
at least partially via expansion of the supplementary coolant.
6. The gas turbine engine (20) of any preceding claim, wherein the supplementary coolant
injector (140...444) comprises a plurality of supplementary coolant ports, each of
said supplementary coolant ports being configured to inject a portion of a or the
supplementary coolant into said at least one cooled cooling air path (110...414).
7. The gas turbine engine (20) of any preceding claim, wherein the at least one compressor
bleed (320; 322; 420, 422, 424) comprises at least a or the first compressor bleed
(320...424) connected to a first cooled cooling air path and a or the second compressor
bleed (320...424) connected to a second cooled cooling air path, and a first supplementary
coolant connected to the first cooled cooling air path is a liquid, and a second supplementary
coolant connected to the second cooled cooling air path is a compressed gas, optionally
wherein the first supplementary coolant is configured to cool coolant in said first
cooled cooling air path at least partially via a state change of the supplementary
coolant.
8. The gas turbine engine (20) of any preceding claim, further comprising an engine controller
(160; 260; 360; 460) controllably coupled to said supplementary coolant injector (140...444)
and configured to control injection of the supplementary coolant through the supplementary
coolant injector (140...444), optionally wherein the controller (160...460) includes
a memory storing instructions configured to cause the controller (160...460) to operate
the injector (140...444) at a first injection level during a first engine mode of
operations, and at a second injection level during a second mode of engine operations.
9. The gas turbine engine (20) of any preceding claim, wherein the at least one cooled
cooling air path (110...414) includes a heat exchanger configured to cool bleed air
passing through the at least one cooled cooling air path.
10. The gas turbine engine (20) of any preceding claim, wherein a supplementary coolant
contained in said coolant supply comprises at least one of a compressed gas, water,
liquid nitrogen, liquid CO2, and liquid air.
11. A method for cooling air in a cooled cooling air system comprising:
injecting at least a first supplementary coolant into a first cooled cooling air path
(110; 210; 310, 312; 410, 412, 414), and thereby cooling a coolant passing through
the cooled cooling air path (110...414), the supplementary coolant including a compressed
gas; and
providing the cooled cooling air to at least one flowpath component of a gas turbine
engine.
12. The method of claim 11, further comprising injecting a second supplementary coolant
into a second cooled cooling air path, optionally wherein the first supplementary
coolant includes a compressed gas and the second supplementary coolant is one of a
compressed gas distinct from the first compressed gas and a liquid.
13. The method of claim 11 or 12, further comprising receiving coolant into the first
cooled cooling air path from at least one compressor bleed (120...424), optionally
wherein the compressor bleed (120...424) is one of a mid stage compressor bleed (220;
320; 422) and a compressor outlet bleed (120; 322; 420, 424).
14. The method of any of claims 11 to 13, further comprising cooling air in the first
coolant path using a heat exchanger.
15. The method of any of claims 11 to 14, further comprising varying an amount of the
first supplementary coolant injected into the first cooled cooling air path using
a controller (160...460), with the amount of coolant injected being dependent upon
a current engine mode of operations.